The danger of exposure to chemical or biological agents can be severe. Whether a result of unintended release by way of, e.g., an accident, or intentional delivery, it is desirable to quickly and accurately identify (1) the type of agent that has been released and (2) the precise area of contamination. Early and accurate detection of such dangerous substances can be a significant factor in reducing potential casualties and limiting further spreading of the agent, e.g., by wind, human and animal contact, etc.
In recent years, there has been an increased interest in developing and deploying nuclear, biological, and chemical (NBC) sensor technologies to quickly identify unknown substances, contaminants, and agents, even at very low concentrations. Some of these technologies are designed to measure surface-deposited contamination and use vehicles and associated test equipment to retrieve a physical sample of the contaminant and then employ extremely cumbersome and time-consuming processes based on a mechanical sampling wheel system to test for agents.
In view of the complexity of such approaches, newer, simpler, safer and more reliable technologies have been in demand. One emerging technology in response to this desire is referred to, generally, as “standoff surface detection,” and refers to a category of technologies that permit detection of substances without actually having to physically come in contact with the substance of concern. The goal of these detection systems is to provide the capability to detect, identify, locate, quantify, warn, and report chemical or biological threats and thereby give military forces or civilian personnel sufficient early warning to avoid (further) contamination.
An example of a standoff surface detection system is a technology known as Laser Interrogation of Surface Agents (LISA) that has been developed by ITT (Wilmington, Del.). LISA uses a laser and associated sensor attached to a reconnaissance vehicle that looks for chemical agents on the ground (or any surface) using a technique known as Raman Scattering (or Raman Effect), which is an optical property that can be exploited to identify known chemical agents. Current ITT LISA systems have standoff ranges from 0.4 to 3 m and can provide detection on each single laser shot or pulse, at 25 pulses per second. This allows personnel manning the vehicle with the ability to perform on-the-move, real-time measurements of chemical agents on the ground. The LISA technology also provides detection teams the ability to create or generate a map with chemical agent contours that build up as detection is taking place.
Standoff biological agent detection is significantly more difficult than chemical detection. Specifically, it is difficult to discriminate and measure biological agents from naturally occurring background materials. Moreover, real-time detection and measurement of biological agents in the environment can be daunting because of the number of potential agents to be identified, the complex nature of the agents themselves, the countless number of similar microorganisms that are a constant presence in the environment, and the minute quantities of pathogen that can initiate infection. Potential biological agents can also disguise themselves in benign entities.
In light of these obstacles, approaches for detecting biological agents differ somewhat from those technologies that are employed to detect chemical agents. While the molecules that comprise biological agents are extremely complex and large in comparison to chemical agents, they are only made up of a very limited number of unique building blocks. As a result, it has been found that it is necessary to use a laser with very specific ultra-violet wavelengths to probe the biological agent in order to enhance its Raman signal.
In sum, whether for detection of chemical substances or biological substances, Raman spectroscopy is an evolving complex art and those skilled in the art appreciate that a Raman sensor along with its supporting equipment is a complex and sensitive apparatus even under the best of circumstances, such as under controlled laboratory conditions. Keeping such an apparatus operating properly in the field presents an even greater challenge. There is thus a need to provide improved Raman spectroscopy equipment and methods of operation thereof in order to effectively bring standoff surface detection to practical use, and particularly for extended field use.